Rotary stamping apparatus and method of forming sheet metal

ABSTRACT

A rotary stamping apparatus for forming moving sheet metal and having a die assembly moveable forward and backward along a linear path, with upper and lower dies on respective sides of the sheet metal, the dies being closeable on the sheet metal for forming, and, a rotary drive crank system coupled to the die assembly, and operable to move the die assembly forward and backward along the linear pat, and being further operable to close the dies the sheet metal. Also disclosed is a method of forming moving sheet metal by such apparatus.

This application claims priority of U.S. Provisional Application Ser.No. 60/711,679, filed Aug. 29, 2005, Inventor E R Bodnar, TitleECCENTRIC ROTARY STAMPING APPARATUS & METHOD OF FORMING SHEET METAL.

The invention relates to rotary stamping apparatus employing flyingdies, for forming sheet metal moving along a forming path, and to amethod of forming sheet metal.

BACKGROUND OF THE INVENTION

Apparatus for stamping and forming sheet metal moving along a movementpath in the past, has employed flying dies, moving along rails, oneither side of the sheet metal. Other forms of moving die apparatus haveemployed dies mounted on a rotary core, with the dies moving around amore or less circular path.

The rotary moving die apparatus is of complex design, and requires greatprecision in the control of movement. Flying dies moving to and fro onrails, are easier to design and build and control, because the movementof the die is linear instead of rotary. The rotary type of moving dieapparatus seems to offer some advantages in that the rotation of therotors carrying the dies is continuous in one direction. By contrast themovement of flying dies moving on rails is necessarily a reciprocation,from forward to stop to reverse to stop to forward and so on. One of theproblems in the design of flying dies moving on rails, is that the dies,and their associated die plates and movement mechanism represents afairly heavy mass of metal, and that entire mass must be acceleratedfrom zero, to the line speed of the sheet metal and then stopped,reversed and reaccelerated again. In one highly successful form offlying shear, designed by the present inventor, the acceleration wasachieved by a pneumatic cylinder and the reverse movement was achievedby a gear and a rack system.

It has now been found that in the flying die system, the forward andreverse movement can advantageously achieved through a continuouslyrotating crank. This form of movement reduces the mass of metal partswhich must be starting and stopping, since the movement is achievedthrough a continuously rotating crank. With this improvement, the flyingdies can be operated at a much higher line speed, enabling the runningof the complete sheet metal production line at a greater efficiency.

BRIEF SUMMARY OF THE INVENTION

The invention provides a rotary stamping apparatus for forming movingsheet metal with dies which are driven to and fro by a rotary crank,thereby achieving a much higher line speed than was possible withearlier apparatus.

The invention provides a stamping apparatus in which one of the formingdies are moveable in a linear direction along rails, parallel to thesheet metal moving on the production line, and in which the other diemoves on an arcuate path, and in which the drive and power mechanism forthe dies comprises a form of a rotary crank device.

A speed adjustment mechanism is incorporated for correcting slightmismatching between the line speed of the metal and the speed of thedies.

Preferably there are upper and lower dies forming a die assembly, theterms upper and lower simply indicating dies on opposite sides of thesheet metal. The upper die is moved by a rotary drive along a generallyarcuate path, and the lower die is moved by a drive along a linear path,the drives being connected to ensure movement of the dies in unison andin registration with one another.

The drive transmission for the upper die is an eccentric rotary driveand the drive transmission for the lower die is a rotary crank in theform of a cam follower which drives the lower die to and fro along itslinear path the two drives being connected and driven by a common primemover.

The invention also provides a method of forming sheet metal, using suchapparatus.

For a better understanding of the invention, its operating advantagesand specific objects attained by its use, reference should be made tothe accompanying drawings and descriptive matter in which there areillustrated and described preferred embodiments of the invention.

IN THE DRAWINGS

FIG. 1 is a general perspective illustration of a form of apparatus;

FIG. 2 is an end elevation of the apparatus;

FIG. 3 is a side elevation of the apparatus;

FIG. 4 is a perspective of the rotary housing surrounding the crankshaft, and,

FIG. 5 is a schematic side elevation showing movement of the housing inphantom.

DESCRIPTION OF A SPECIFIC EMBODIMENT

The drawings illustrate a rotary stamping apparatus (10). A lower die(12) is mounted on lower die bed (14). An upper die (16) is mounted onupper die bed (18). The upper and lower die beds are connected by dieposts (20). The upper and lower dies and die beds thus form a singlemoveable die assembly, which moves forward and back as one along thepath of the sheet metal (below).

The sheet metal on the production line is indicated in phantom as (M).

The drive mechanism is illustrated generally as the shaft (22) driven bya suitable prime mover (P). The upper die bed (18) is carried by cranks(24) on the shaft (22). The cranks (24) have bearings (26) for agenerally cylindrical housing (28). Housing (28) is welded to a supportplate (30) by means of forward and rear arms (32-32). Upper die bed (18)is carried by support plate (30) on sliders (described below).

As the shaft rotates, the crank (24) orbits around an annular path, thehousing (28), riding on bearings (26) orbits with the crank, but thecrank rotates within the housing for reasons described below.

Lower die bed (14) is carried on lower slide rails and gibbs (38), whichare in turn supported on suitable columns. Thus a set of forming diescan be mounted on the upper and lower die beds, for forming variousdifferent shapes sequentially in the sheet metal. These may be simpleblanked out openings, but will usually be openings with indentations,and formed sections and flanges.

The upper die bed (18) is carried beneath support plate (30) on upperrails or slides and gibbs (40), shown in phantom in FIG. 3, similar toslides and gibbs (38).

As the cranks orbit, they will carry the housing with them, but beinglocated within the housing, the housing (28) will orbit. The housingwill thus carry with it the support plate (30) and the upper die bed(18) will move around what is essentially an arcuate path, forwardly andrearwardly.

The upper die bed (18) is coupled to the lower die bed (14) by means ofposts (20). However the lower die bed (14) does not move upwardly anddownwardly, but moves along a linear path. In this way the upper die bedmoves along an arcuate downward path and closes towards the lower diebed and then the upper die bed moves along an arcuate upward path andopens again, thereby releasing the formed sheet metal. Thereafter theupper die bed and lower die bed move rearwardly in unison.

The movement of the lower die bed (14) along its linear path is assistedby a rotary drive (described below) coupled to prime mover (M).

Since the movement of the housing (28) is rotary, around an orbit, itwill be appreciated that the linear speed imparted to the die assemblyby means of its movement will vary. Similarly the rotary drive for thelower die bed (below) is a such that the linear speed imparted by itwill also vary from start to stop and back again. As a result, thelinear speed of the die assembly is not constant. The speed depends uponthe rotational position of the housing (28).

At the 180° bottom dead centre, the linear speed of the die assemblywill correspond to the linear speed of the metal M. At 0° top deadcentre the linear speed of the die assembly will be opposite and equalto the speed of the sheet metal. At 90° and 270° the linear speed of thedie assembly will be zero, relative to the sheet metal. From 270° to 90°the die assembly moves in reverse, rearwardly.

Between 90° and 180° the linear speed of the die assembly relative tothe sheet metal will gradually increase. From 180° to 270° the linearspeed of the die assembly will then gradually decrease.

In order to compensate for this change in linear speeds, speedadjustment ramps (42) ad (44) are incorporated (FIGS. 1 and 2 and 5).Lead ramps (42) have generally arcuate profiles to engage rampsfollowers (46) as the die assembly closes. The trailing ramps (44) arelocated to engage ramp followers (46) on the upper bed die so as toengage followers (46) as the dies open.

Four ramp followers (46) in the form of rollers are mounted on the upperdie bed (18). As the upper die bed (18) is moved downwardly by thehousing (28) from three o'clock, closing towards the six o'clockposition, the ramp followers will engage the lead ramps (42). The upperdie bed (18) will speed up also moving the lower die bed (14) and startmoving by sliding on gibbs (38) in the linear direction, faster than thelinear speed of the housing (28). As the housing reaches the six o'clockclosed position, the followers (46) will leave the ramps (42) and thedie beds (18) and (14) and upper and lower dies will be moving at thelinear speed of the sheet metal. As the housing rotates further fromseven to eight towards nine o'clock the dies open. The ramp followers(46) will engage trailing ramps, (44) and move the die bed (18) and (14)faster than the linear speed of the housing. In this way the linearspeed of the dies matches the linear speed of the sheet metal.

As the upper die closes on the lower die approaching 180° the followers(46) disengage from the ramps (42). After passing through 180° (sixo'clock) the followers (46) engage the trailing ramps (44) and maintainspeed. In this way, while the dies are actually closing on the sheetmetal and opening once more, the linear speed of the dies in the dieassembly is maintained exactly equal to the linear speed of the sheetmetal. This ensures clean forming of the sheet metal and avoids damageto the dies.

It will be understood that the adjusting effect of the ramps takes placeonly just before closing, and from just after closing to just afterseparation. The amount of the actual adjustment results in a movement ofthe die assembly by only a fractional distance. This will largely dependon the gauge of the sheet metal, with a larger gauge requiring somewhatmore adjustment, and a thinner gauge requiring less. It will also dependon the depth of the formations being indented into the sheet metal. Thedeeper the two dies have to interengage, the longer they will be incontact with the sheet metal, therefor the speed must be match over alonger distance in the linear direction of travel.

In order to power and assist the forward movement of the lower die bed(14), the lower die bed (14) is provided with a rotary drive shaftindicated generally as (50). This drive shaft is connected to cams (52).Cams (52) engage bars (54) connected to lower die bed (14). As the driveshaft (50) rotates, the cams (52) orbit through 360°. As they orbit, thecams will drive the lower die bed (14) forward and then backward oncemore. Drive shaft (50) is driven by gears (56), from prime mover (P).

In order to permit the lower die bed (14) and lower die to move andmatch the speed of the sheet metal, there is a slight degree ofclearance between cams (52) and bars (54). In this way when the upperdie bed (18) is moved by ramps (42) and (44) the lower die bed (14) willalso move with the upper die bed (18).

In this way, both the upper and the lower dies and die beds are drivenand forwardly and then backwardly together in unison. The ramps andfollowers may also assist in holding support plate (30) and die bed (18)level and parallel to die bed (14) before, during, and after contactwith the sheet metal, although this function is achieved primarily byposts (20).

The foregoing is a description of a preferred embodiment of theinvention which is given here by way of example only. The invention isnot to be taken as limited to any of the specific features as describedbut comprehends all such variations as come with in the scope of theappended claims.

1. A rotary stamping apparatus for forming moving sheet metal andcomprising; a die assembly moveable forward and backward on oppositesides of the sheet metal, having upper and lower dies on respectivesides of the sheet metal, the dies being closeable on the sheet metalfor forming thereof; a rotary drive crank system coupled to the dieassembly, and operable to move said die assembly forward and backwardalong said linear path, and being further operable to close said dies insaid die assembly on said sheet metal; the die assembly being moveablein a linear direction along rails parallel to the sheet metal: bearingson driving the rotary crank, and a housing being carried on saidbearings for rotating relative to said rotary crank; a speed adjustmentmechanism in the form of arcuate drive ramps and followers therefor, onsaid die assembly connecting with said ramps and being operable forcorrecting slight mismatching between the line speed of the metal andthe linear speed of the die assembly, during closing and opening of saiddies.
 2. A drive rotary stamping apparatus for forming moving sheetmetal as claimed in claim 1 wherein said housing is carried as part ofthe rotary crank system, being generally cylindrical and a support platemember secured on said housing, and said upper die bed being mounted onsaid support plate, and said support plate and said upper die bed movingalong a generally arcuate path forwardly and rearwardly.
 3. An eccentricdrive rotary stamping apparatus for forming moving sheet metal asclaimed in claim 2 and including, slide rail members and slides on andsaid support plate, whereby said upper die bed is slidable in a lineardirection to and fro along said support plate.
 4. A rotary stampingapparatus for forming moving sheet metal as claimed in claim 2 andincluding; a lower die bed for supporting said lower die, and sliderails and slides supporting said lower die bed whereby said lower diebed is slidable to and fro.
 5. A rotary stamping apparatus for formingmoving sheet metal as claimed in claim 4 and including; a lower drivesystem coupled to said lower die bed, and being operable to move saidlower die bed forwards and backwards along said slide rails and slides.6. A rotary stamping apparatus for forming moving sheet metal as claimedin claim 5 and including; leading ramp members, for engaging followers,as said upper die bed is moving downwardly, and trailing ramp membersfor engaging said followers as said upper die bed is moving upwardly,said leading and trailing ramp members procuring movement of said upperdie bed relative to said upper support plate, whereby to match the speedof said die assembly with the speed of movement of said sheet metal. 7.A rotary stamping apparatus for forming moving sheet metal as claimed inclaim 6 including slide posts connecting said upper and lower die beds,whereby said upper and lower dies may close and open, with one said diebed sliding along said posts, and wherein said first and second drivesystems are coupled to a single prime mover and so as to drive both saidupper and lower die beds in the same direction simultaneously, and inregistration with one another.
 8. A method of forming moving sheetmetal, using apparatus having a die assembly moveable forward andbackward on opposite sides of the sheet metal, the dies being closeableon the sheet metal for forming thereof, and including the steps ofmoving said die assembly along said forward and backward path by meansof a rotary crank coupled to the die assembly; closing said dies in saiddie assembly on said sheet metal by the operation of said rotary crankthereby forming said sheet metal while said sheet metal is moving; and,adjusting the forward speed of the die assembly at a point just beforeclosing of the die assembly and maintaining such speed until a pointjust after die opening, whereby to match the speed of the die assemblywith the sheet metal.
 9. A method of forming moving sheet metal, asclaimed in claim 8 and including the steps of moving a first die on oneside of said sheet metal along a generally arcuate path, andsimultaneously moving a second die on the opposite side of said sheetmetal along a linear reciprocal path, and simultaneously reciprocatingsaid first die towards and away from said second die, for forming andreleasing said sheet metal.
 10. A method of forming moving sheet metal,as claimed in claim 9 and including the steps of driving said first die,by a first rotary drive system and including driving said second die, bya second rotary drive system coupled to said first drive system andwherein said first rotary drive system drives said first die around saidgenerally arcuate path, and wherein said second rotary drive systemdrives said second die along said linear path, thereby moving said firstand second dies in unison along two different paths.
 11. A method offorming moving sheet metal, as claimed in claim 10 and including thesteps of adjusting the linear speed of said first and second die beds ata point just before closing on said sheet metal, and from closing to apoint just after opening, whereby to match the linear speed of the sheetmetal, during closing and opening of said dies.